Add MySQL to goldeneye: generate relations.jsonl and check the analyze cases against a live server

[kyleconroy]

Summary

Adds a mysql engine to internal/goldeneye, following the pattern of the other engines: Locate, Version, Generate and Analyze, tests that run the checks, and a job in the gen workflow. The server is named by MYSQL_SERVER_URI (a go-sql-driver DSN) and has to be MySQL 26, the major pinned in mysql.Major; the workflow runs the mysql:26.7 image.

What is generated

MySQL keeps no catalog of its types, functions or operators, so those files stay hand-written, the way ClickHouse's and SQLite's do. What it does describe is its data dictionary: internal/engine/dolphin/dialect/relations.jsonl is now generated from information_schema — every view of it, with columns, NOT NULL and the declared type spelled MySQL's way (bigint unsigned included). Names are written in lower case, since MySQL matches them in any case and the dolphin converter lowercases every identifier. The other schemas mysqld --initialize creates (mysql, performance_schema, sys) are base tables, and every table a dialect seeds is one the analysis core hands codegen as a model, so they are left out for now.

Two hand-written files change alongside:

• types.jsonl gains <type> unsigned aliases on the numeric types, so the generated columns resolve to their base type instead of a user type.
• functions.jsonl marks the aggregates that are NULL over no rows as nullable (AVG, MAX, MIN, SUM, STD*, VAR*, JSON_ARRAYAGG, JSON_OBJECTAGG), which is what MySQL reports; BIT_*, COUNT and ANY_VALUE are not. Their return type is any, so no generated Go changes; analyze_select/mysql's golden gains a nullable on max(created).

The analysis check

Analyze loads a case's schema and fixture into a database of its own and asks the server three things about each query:

• What a driver sees: the query is run with every parameter a user variable set to NULL, and result columns come from the result set's metadata as go-sql-driver reports it.
• What the resolver made of it: the optimizer trace's expanded_query prints each query block after name resolution and before optimisation, with every column qualified, aliases kept and SELECT * expanded, which gives provenance and each parameter's partner. Views and derived tables are kept unmerged so a column read through one is reported as its column, and an information_schema view is not resolved away into the dictionary tables behind it.
• For statements the trace does not expand (INSERT ... VALUES, single-table UPDATE/DELETE), the note EXPLAIN FORMAT=TRADITIONAL leaves, which prints the statement the same way. A SELECT cannot be read from the note: it is printed after optimisation, and a unique-key lookup against an empty table has folded to NULL = (@x) there.

MySQL reports nothing about a parameter but its position, so a parameter is described by its partner: a column's type and nullability from information_schema, a derived table's column from what its block projects, an expression's from running it over the tables it reads. Two things the driver keeps to itself, and how the check works around them: the table a result column comes from (read from the trace), and the length that distinguishes the sizes of TEXT/BLOB on the wire (a column read from a table is spelled the way the table declares it).

All five MySQL analyze cases match the server byte for byte, including a new analyze_system_catalog/mysql case that exercises the generated relations end to end through sqlc analyze.

Also

• endtoend.Rewrite now recognises sqlc.slice(...), and hands LIMIT to the second count of LIMIT ?, ?.
• The engine table in the command gains a dir, since MySQL's dialect lives under dolphin.
• README and CLAUDE.md describe the new engine.

Test plan

• go test ./... in internal/goldeneye with MYSQL_SERVER_URI set: dialect and all five analyze cases match MySQL 26.7.0 (goldeneye check mysql says the same)
• go test ./internal/... ./cmd/... in the main module, including TestReplay/base for every MySQL case
• The analysis check exercised on a scratch case with BETWEEN, IN lists, NOT LIKE, function partners, LIMIT ?, ?, derived tables, correlated subqueries, multi-row INSERT without a column list, ON DUPLICATE KEY UPDATE, multi-table UPDATE, LEFT JOIN, UNION and a recursive CTE

🤖 Generated with Claude Code

https://claude.ai/code/session_012DTeySVan5NcA3RS6xxdUn

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Generated by Claude Code